This invention relates to a tomographic apparatus for producing transversal layer images of a subject, comprising an x-ray measuring arrangement with a transmitting arrangement for emitting x-rays and a radiation receiver arrangement which determines the intensity of radiation behind the subject, and a drive system for the measuring arrangement with a rotating frame for producing rotational movements of the x-ray measuring arrangement, means being included for transforming the signals supplied by the ray receivers into a layer image.
A tomographic apparatus of this type is described in German Offenlegungsschrift No. 1,941,433. So far as the measuring arrangement is concerned, it is known from this particular publication to use a single x-ray tube and a single ray detector and to displace the measuring arrangement after each rotational movement through a small angle, along a straight line path perpendicular to the central ray of the x-ray beam to effect a scanning of the subject. In this known arrangement, therefore, rotational movements through small equal angles and linear scanning movements follow one another in an alternating sequence. However, it is also known that the displacement can be dispensed with, providing the ray receiver is made up of a plurality of ray detectors whose signals are simultaneously processed, and providing the x-ray beam is fan-shaped so as to strike all of the detectors simultaneously.
A disadvantage of the known tomographic apparatus is that the time required to build up an x-ray image is relatively long because the measuring arrangement has to be rotated through 180 degrees in the case where it is linearly displaceable, or through 360 degrees in the case where a row of detectors is used in conjunction with a fan-shaped x-ray beam.